1. Field of the Invention
The present invention relates to the field of high strength, high pressure, high temperature, corrosion and erosion resistant structures and their methods of manufacture. More particularly, this invention relates to structures which are capable of withstanding heavy loads and elevated temperatures and pressures for extended periods of time. Such structures are of particular interest in the field of gun tubes including projectile launchers.
2. Description of the Prior Art
It had been extremely difficult to produce structures which can retain structural integrity and not corrode or erode when exposed repeatedly to high pressure gases at temperatures in excess of 2,000 degrees Celsius. Materials that do not easily corrode or erode do not have the structural strength and ductility to withstand substantial thermal and structural stress. Conversely, materials which can withstand substantial thermal and structural stress are generally subject to rapid erosion and corrosion.
These materials limitations had substantially hampered achievement of maximum performance and component life in a number of fields, notably ordnance. Propellants used in ordnance include, for example, HDX and RDX double-base and composite propellants. Gun tubes, for example, are used in most artillery systems including small arms, anti-aircraft guns, anti-tank weapons, mortars and missile launchers. Gun tubes are subjected to multiple shots over their lifetimes. Machine gun tubes, for example, are very often exposed to hundreds of shots per minute. Each shot subjects the tube to high thermal shock and gas pressures as the shell fires and high structural loads as each projectile accelerates down the tube. Under these conditions brittle materials tend to fail rapidly. Even ductile materials have poor service life and reliability.
To achieve optimum projectile velocity and system performance the temperature of the propellant gasses may be as high as 3000-3400 degrees Celsius and gas pressures may be as high as 60,000 to 150,000 pounds per square inch. It had been found that if shells are made with optimum propellant chemistries catastrophic failure of the gun tubes occurs in a very few minutes, often with only from 100 to 1,000 shots. If shells are made with close to optimum propellant chemistries gun tubes wear out more rapidly, thus limiting their useful lives. It had been necessary in practice to make artillery shells with much less than optimum propellant chemistries so as to keep the operating temperatures and heat fluxes within the limits of the gun tube materials. As a consequence projectile velocity and performance had been severely limited: one consequence had been limitation of the maximum number of rounds which can be fired.
Improving the temperature capabilities of gun tubes would substantially improve ammunition and system lethality. The lives of gun tubes, that is the maximum number of rounds which can be fired, would be extended resulting in considerable financial savings.
Applications exist outside the armament field for structures which are capable of withstanding shock and high structural loads in highly corrosive, high temperature environments. The absence of such structures limits or precludes the use of some reactions in the chemical process industry. Such structures would also be useful in the propulsion field (e.g. rockets and arc-jets) as well as in the nuclear and metallurgical industries. Such structures could, for example, find great utility in fiber and wire drawing machines, shock tubes and plasma arc equipment.
Development of a material which can retain structural integrity and shows minimal weight, dimensional, microstructural, or other compositional changes when exposed to high temperatures and high pressures would represent a great improvement in the field of materials engineering. Such a material would satisfy a long felt need of ordnance, nuclear, metallurgical and other engineers.